configure: Disable -Wmaybe-uninitialized by default

It is by definition unreliable and causes pointless noise on valid
code.

configure

@@ -3907,6 +3907,7 @@ check_cflags -Wundef
 check_cflags -Wmissing-prototypes
 check_cflags -Wstrict-prototypes
 enabled extra_warnings && check_cflags -Winline
+enabled extra_warnings || check_cflags -Wno-maybe-uninitialized
 
 # add some linker flags
 check_ldflags -Wl,--warn-common